Magnetic Field of a Straight Wire Calculator
Enter the current and distance to find the magnetic field.
Result
How to use
- Enter your values in the fields above.
- Press Calculate to see your result instantly.
- Use the Share button to copy a link to your result.
About this calculator
Ampère's law shows that a long, straight wire carrying a steady electric current generates a magnetic field that circles the wire, with a strength given by B = μ₀I/(2πr), where I is the current, r is the distance from the wire, and μ₀ is the permeability of free space. The field is strongest close to the wire and weakens in inverse proportion to distance.
This calculator computes that flux density in tesla, along with the more practically-sized microtesla and gauss units, from any current and distance you enter. It's a foundational formula in introductory electromagnetism courses, used to build intuition before tackling solenoids and Biot–Savart law problems, and it's also applied by electrical engineers estimating stray magnetic fields near power cables or busbars for safety and interference assessments.
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